1. Field of the Invention
This invention relates to amplifiers. More particularly, this invention concerns an amplifier of simple design which is formed as part of an integrated-circuit (IC) chip and provides high loop gain as well as other desirable characteristics.
2. Description of the Prior Art
A wide variety of circuit designs have been used for amplifiers formed on IC chips. Operational amplifiers are employed extensively, and usually comprise a differential input stage and a single-ended output stage. Commonly, an active load such as a PNP current mirror will be coupled to the collectors of the differential-stage transistors. The single-ended output of the current mirror can drive one or more voltage-gain stages.
Although such amplifiers have served many practical purposes, their performance is not fully satisfactory in certain respects. For example, the gain of prior amplifiers tends to vary to an undesired degree with changes in load, e.g. due to variations in ambient temperature. Still other aspects of prior amplifier designs require improvement to meet the needs of modern precision linear components.